In semiconductor manufacturing, wafers and other substrates are transferred among various process chambers using robotic handlers. One of the enduring challenges of wafer handling is the need to locate wafers or wafer centers with sufficient precision to permit accurate placement and processing within the process chambers. In general, semiconductor manufacturing systems employ various beam-breaking sensor arrangements to “stripe” passing wafers and detect the wafer edges. This data can be used, in turn to locate a wafer center relative to a robotic handler so that subsequent movement and placement can be more accurately controlled. Center finding is sufficiently important to fabrication that this process is routinely calibrated and repeated throughout the processing of each wafer.
While numerous physical sensors and processing algorithms have been devised for centering wafers in a semiconductor manufacturing process, there remains a need for improved wafer center finding techniques that reduce the number of sensors required or improve the simplicity and/or accuracy of center finding calculations.